Independence, MO, USA
N6149B
CESSNA T210M
The pilot reported that he was in cruise flight when the engine began to run rough and lose power. Smoke began to enter the cockpit, and engine oil covered the windshield. The engine ultimately lost all power. The pilot executed a forced landing to a roadway, and the left wing struck a bridge guardrail. Examination of the engine revealed a fatigue failure of the crankshaft initiating at the No. 6 connecting rod journal. Further examination determined that several crankcase main bearing saddles were oversized compared to the required specifications. As a result, the crankshaft was not adequately supported within the crankcase during operation, which precipitated the fatigue failure of the crankshaft. Records indicated that the engine was initially manufactured with one oversized saddle bore. The manufacturer subsequently rebuilt the engine, which was installed on the accident airplane. At the time of the accident, the engine had accumulated 1,303.5 hours since it was rebuilt.
HISTORY OF FLIGHT On February 24, 2011, about 0145 central standard time, a Cessna T210M, N6149B, was substantially damaged during a forced landing following a loss of engine power in cruise flight near Independence, Missouri. The pilot made a forced landing to a roadway. The airplane was registered to and operated by Flight Express Inc. under the provisions of 14 Code of Federal Regulations Part 135 as an on-demand cargo flight. Night visual meteorological conditions prevailed and no flight plan was filed. The pilot sustained minor injuries. The flight originated from St. Louis Downtown Airport, Cahokia, Illinois, about 0030. The intended destination was Charles B. Wheeler Downtown Airport (MKC), Kansas City, Missouri. The pilot reported that he was in cruise flight at 4,000 feet mean sea level, about 18 miles from the intended destination, when the engine began to run rough and lose power. Smoke began to enter the cockpit and engine oil covered the windshield. The engine ultimately lost all power. The pilot executed a forced landing to a roadway. The left wing struck a roadway bridge guard railing during the landing. PERSONNEL INFORMATION The pilot held an airline transport pilot certificate with single and multi-engine land airplane ratings. He also held a flight instructor certificate with single and multi-engine airplane and instrument airplane ratings. He was issued a first class airman medical certificate on March 1, 2010. The pilot reported that at the time of the accident, he had accumulated about 5,800 hours total flight time, with approximately 900 hours in Cessna 210 airplanes. His most recent flight review was completed on December 4, 2010. AIRCRAFT INFORMATION The accident airplane was a 1978 Cessna T210M, serial number 21062694. It was configured with one pilot seat to facilitate cargo operations. The airplane was powered by a 300-horsepower Continental Motors IO-550-P8B engine, serial number 821115-R. The operator reported a total airframe time of 12,103.0 hours at the time of the accident, with 88.3 hours since the most recent inspection. The engine had accumulated 1,303.5 hours at the time of the accident. The most recent inspection was completed on January 3, 2011, at 12,014.7 hours total airframe time. An engine oil change was completed on January 31, 2011. Maintenance records indicated that the engine was rebuilt by Continental Motors and installed on the accident airplane in March 2009. METEOROLOGICAL INFORMATION Weather conditions recorded at the Charles B. Wheeler Downtown Airport (MKC), located about 14 miles west of the accident site, at 0154, were: wind from 030 degrees at 7 knots; 10 miles visibility; overcast clouds at 6,000 feet above ground level; temperature 5 degrees Celsius; dew point 1 degree Celsius; altimeter 30.01 inches of mercury. Weather conditions recorded at the Lee’s Summit Municipal Airport (LXT), located about 10 miles south-southwest of the accident site, at 0153, were: wind from 040 degrees at 7 knots; 10 miles visibility; overcast clouds at 5,000 feet above ground level; temperature 4 degrees Celsius; dew point 2 degrees Celsius; altimeter 30.01 inches of mercury. WRECKAGE AND IMPACT INFORMATION The airplane came to rest on a roadway after the forced landing. The left wing struck a guard railing, resulting in substantial damage. Specifically, the lower left wing skin was cut across approximately the entire chord of the wing. Two of the impact cuts were located near the wingtip; the third was near mid-span outboard of the pitot tube. The contact with the guard rail also caused associated damage to the wing substructure in the area of the wing skin damage. TESTS AND RESEARCH A teardown engine examination was conducted under the direct oversight of the NTSB. The crankcase exhibited an approximate 4 inch by 8 inch opening forward of the No. 5 cylinder bore and extending above the No. 6 cylinder bore. The crankshaft was fractured between the No. 6 connecting rod journal and the No. 4 crankshaft main journal. The No.4 main bearing was observed to be shifted within the crankcase saddle. The No. 3 main bearing was fractured into multiple pieces, most of which were recovered from the oil sump. The camshaft was fractured at two locations; between the No. 6 intake and exhaust lobes, and common to the No. 3 main journal. The No. 6 connecting rod bolts were fractured. The No. 6 connecting rod was deformed and exhibited gouges consistent with secondary mechanical damage. The No. 5 and No. 6 pistons exhibited damage consistent with secondary mechanical impact. Specifically, portions of the skirt areas on both pistons were separated from the remainder of the associated piston. Piston fragments were recovered from the oil sump. This damage was also consistent with secondary mechanical impact. The crankshaft fracture surfaces exhibited features consistent with fatigue initiating at the forward radius of the No. 6 connecting rod journal. Three additional cracks were also observed initiating at the forward flank of the No. 3 main journal, the forward flank of the No. 4 connecting rod journal, and the aft flank of the No. 5 connecting rod journal. The camshaft fracture surface features were consistent with fatigue caused by reverse bending. Failure of the No. 6 connecting rod bolts was consistent with overstress. Records indicated that the No. 3 crankcase main saddle bearing diameter was oversize by 0.0017 inch when it was originally manufactured. The crankcase was subsequently reconditioned by the manufacturer for use in the rebuilt engine. The manufacturer’s engineering documentation related to reconditioned crankcase saddle bores noted that the diameter may exceed the specified limit by 0.002 inch within a 40-degree arc centered on the splint line of the crankcase. Outside of that area the diameter must conform to the dimensional requirements. Measurements of the crankcase saddle bores revealed oversize diameters at multiple locations. At a point oriented 90 degrees to the crankcase split line, all saddle bore diameters measured within specifications. At saddle bores No. 1, No. 4, and No. 5, one of the diameter measurements taken at either the plus or minus 20-degree limit from the split line was oversized. At the No. 2 and No. 3 saddle bores, the diameter was oversized at both the plus and minus 20-degree limit. The maximum dimension, located on the No. 3 bore diameter, measured 2.8185 inch and was 0.0015 inch over the dimensional limit.
Latent dimensional discrepancies related to the engine crankcase main bearing saddle bores, which precipitated the fatigue failure of the crankshaft and a complete loss of engine power. Contributing to the accident was the engine manufacturer's failure to properly identify and address the crankcase discrepancies when the engine was rebuilt.
Source: NTSB Aviation Accident Database
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